Process of electrochemical precipitation of metals.



E. R. HOLDEN.

PROCESS OF ELECTROCHEMICAL PRECIPITATION OF METALS.

APPLICATION FILED ocr. o'. me. RENEWEDNOV.5.1917.

1,269,565. PztentedJuno 11, 1913.

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PROCESS OF ELECTROCHEMICAL PRECIPITATION METALS.

APPLICATION HLED 0CT.I0.1916- RENEIWED NOV. 5. 1917.

l ,269,565. Patented June 11, 1918.

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E/EHOL DE'IV.

EDWABD- BOYAL HOLDEN, OF LOS ANGELES, CALIFORNIA.

PBOCESS OF ELECTBOCHEMCAL PRECIPITATION OF METALS.

Specication of Letters Patent.

Patented J une 11, 19

Application filed October 10, 1916, Serial No. 124302. Renewed November5, 1917. Serial No. 200,&56.

To all whom it may concem:

Be it known that I, EDWARD ROYAL HOL- DEN, a citizen of the UnitedStates, residing at Los Angeles, in the County of Los Angelesand Stateof California', have invented new and useful Im rovements in Processesof Electrochemical lrecipitation of Metals, of which the following is aspeciication.

This invention relates to an improved process for electrolyticallyt-reating solutions containing metallic substances and the attainment ofa rapid, economical and eflicient method of precipitating and recoveringnetals from solutions.

This process is more particularly adapted to the precipitation of metalsfrom chlorid, cyanid, sulfate or other dissolving solutions containinggold, silver, v copper or other metals, either single or together. Theessence of this inve'ntion rcsides in the process of distributing anddisseninating an electric current throughout an electrolyte by means ofresistance coils regulating the electric current., hereinafter fully setforth, and illustrated in the accompanying drawings, in which:

Figure 1 is a view in vertical section, partly in elevation, of anapparatus employed in carrying out my process, showing a part of theelectrical device in diagram.

Fig. '2 is a diagrammatic View illustrating the electric circuits andthe nanner of distributing the electric current throughout anelectrolyte.

Fig. 3 is a view in horizontal section on a reduced scale, as seen onthe line 3-3, of Fig. 1.

Fig. 4 is a detail i plan of the revolving resistance coil earriage andthe wiper contact :t'or delivering electric current thereto.

To earry out the action above referred to in the ost advantageousmanner, I preferably use a circular tank of any reasonable number offeet in diameter, and of a depth sufficient to hold large quantities ofsolution containing metale in solution.

ln Figs. 1 and 2 of the accompanying drawing, I have illustrated by avertical section-al View, and in diagram, one embodiment of a tankshowing fully the manner of wiring; the resistance coi"` necessary forthe regulatiou of the current; tne various anodes and their respectivedistances from the cathode; a non-eondueting shaft, said shaft beingconstructed of any suitable material, such as hard Wood, hard rubber orother material, not aifected by acid or alkaline solutions, norelectrolysis, together with a copper, mercury or other negative cathodeon the bottom of the tank.

More specifically in the drawing, A indicates a tank of any suitablematerial, preferably wood, about six feet in diameter, and twelve feetin depth, although' other sizes may be found advantageous. In this tanka vertical shaft B of non-conducting material is mounted, and throughoutits entire height at equal distance apart, carrcs a number of metallicpaddles as anodes nunbered from l to 9: anode 1 being placed just abovea cathode C, conprising a Copper or other me tallic plate or nercuryarranged to cover the bottom of the tank. The paddles are here shown ascomprising four blades to a set; each set consistituting a separateanode. By repcated experiments I have found that in a tank twelve feetdeep filled with a solution containing metals in solution, the bestelectrolytic precipitation is obtaincd when the metallic anodes are setabout twclve to fifteen inches apart; the lowest anode 1 being six totwelvc inches, mere or less, above the cathode C. The shutt is rotatcdby gearing D or other suitable means.

On the upper part of the non-conducting ,sh-aft is a circular nietalliccontact ring E connected with a positive current of clec tricity,through a wiper contact F connected with a conductor G leading from onetel ninal of a source of electrical siupply or gencrator H; a conductorT leading from the other terminal oi' the genertor to the cathode C. Outhe lower end of the metallic contact ring E and attacned thereto isa`circular disk .l of hard rubher or' other nonconducting suhstance,hosting upon and attached to the disk .l are separately wound individualresiriamte coils 1 and 9 as shown in Fig. 2, there, being one resistancecoil for each oi' the :nodes'attachcd to the shaft. The top of eachresistance coil is connected with the contact ring E and the positivecurrent oi electricity passes from the contact ring into each resistancecoil, the lower ends of which are resting on the disk J and each coil isconnected with its own separate insulated wire or conductor 1 to 9,leading down through the electrolyte to an anode. Each one of theseseparate resistance coils is so wired as to convey a regulated andcontrolled Volume of electricity to the anode to which it is attached;the separate coils being graded in decreasing degrees of resistanceaccording to the distance of theanodes :from the cathode, for example,coil l claim as new and useful can be fully under-v stood bv thosedesiring to take advantage of this process.

An experiment was conducted in the above tank which contained 4,500 lbs.of .20% potassium cyanid solution, carrying gold and silverin solution.The solution also contained the necessary amount of sodium chlorid toestablish the conductivity required.

The current was then led throu h the contact ring directly to each anoe, passing thence through the electrolyte to the cathod a for thepurpose of precipitating the gold 4 and silver out of the solution andthis operation continued for six hours. After each hour a sample of thesolution was drawn through a pet cock in the side of the tak just belowanodes 1,' 5 and 9.

The solution obtained below anode 1 at' the end of the first hour,showed that the gold and silver value of 'the solution had decreased 46%per ton of solution. The sample taken simultaneously below anode 5showed that the gold and silver value had decreased.36% per ton ofsolution, while the sample taken simultaneously below anode 9 haddecreased only 6% per ton of solution. Samples taken at the end of thesecond third fourth fifth and sixth hours, showed that theprecipitation' oc curred most rapidly during the first hour, but thatthe action continued proportionately the same during the remaining fivehours at all the respective anodes.

The sampletaken below anode 1 at the end of the sixth or final hourshowed that the gold and silver value of the solution had decreased 982%per ton of solution, while the sample taken simultaneously below anode 5showed the gold and silver value had decreased 75% per ton of solution,while the sample taken simultaneously below` anode 9 had decreasedonly50% per ton of solution. The entire contents of the tank was thenwithdrawn and the solution thbroughly mixed and showed a totalprecipitation of only 74.4: of the gold. and silver fro n the originalsolution.

Anothelexperiment was then made with a similar solution carrying theidentical values in gold and silver per ton; The resistance coils`heretofore described were then put in ;contact on disk J and connectedwith the 'contact ring E and the lead paddles as anodes. The resistancecoils werewound with climax wire in such a manner as to deliver to eachanode the necessary E. M. F. so that the potential at each anode wasaltered and maintained in the electrolyte in proportion to its distancefrom the cathode, thereby regulating the potential between each anodeand the cathode, and producing throughout the solution, from the top tothe bottom,

the required anperage to establish the necessary potentialsimultaneously in all parts of the solution to deconpose and precipitatethe metals from their comgounds, with the following result:

After the above regulated cur'enthad been disseminated throughout theelectrolyte for one hour, samples of the solution correspond 'ing tothose! taken in test one, were drawn just below anodes 1, 5 and 9. Thesolution taken below anode 1 had decreased in value in gold and silver48% per ton of solution. The sample taken simultaneously just belowanode 5 showed the gold and silve rvalue of the solution had decreased44:75 per ton of solution, while the sample taken at the same time, justbelow anode 9 had decreased 35% per ton of solution. Samples taken atthe end of the second-third fourth-fifth and sixth hours showed that theprecipitation was proportionately uniform at all the respective anodes.The samples taken at the end of the sixth or final hour showed that thegold and silver value of the solution had decreased below anode 1, 999%per ton of solution, while the sample taken simultaneously just'belowanode 5 showed the gold and silver value had decreased 993%' per ton ofsolution, while the sample taken simultaneously just below anode 9showed the gold and silver value had decreased 995% per ton of solution.

A continuation of the operation of the current through the electrolytefor a longer !period would have precipitated the trace of gold andsilver remaining in the solution, but the time required and the currentcosts in recovering samecommercially, precluded carrying the operationfurther.

The second table above referred to shows a regulated decrease ofamperage' from the bottom to` the top. The applicant does not desire,however, to limit himself to the method of regulating the amperage sothat the highest amperage is at the bottom and the lowest at the top, asindicated by this table, but may regulate the amperage that rial and thevalues of the table may be reversel, an the highest amperage will be atthe top and the lowest at the bottom, may be substantially equal at eacha'no e. The preferred method is to have the highest amperage at the top,decreasing toward the bottom, but my method broadly contemplatesregulation of the amperage at difl'erent anodes in the solution.

The use of a non-conducting shefit, or one entirely constructed ofnon-conducting matecarrying no current into the electrolyte, makespossible the dissemination of different E. M. F. through various anodesat different points in the solution, with the result above described. i

The above described method of distributing and disseminating an electriccurrent is also adaptable to and greatly accelerates the dissolution ofmetale and their compounds from ores in (for example) a. cyanidelectrolyte by the liberation of cyanogen, at the oathode, according tothe following well known equations:

2AuC -e ect.-current-2Au-2CN(at cathode) 2Cn-2K-2KON thercbyregenerating the solvent solution and mantamng comparatvely unform andconstant strength theren, throu hout the operation, which results inbringing about a very much more rapid and efieent dissoluton of themetals and their compounds than can be obtamed f the electrc current snot distributed and clssemnated by means or the ampera e mesme or" aplurality of anoies throughout the electrolyte.

Similar regeneration of solvent is brought about when bromi, chlorin,sultate solvent is used.

I am aware of the `fact that patents have been ssuecl in this and othercountries *for or other ,z

the use of a current of eleetricity in an else i trolyte containingmetals tor the purpose of clissolution or precipitation, or both, an i Edo not claim anything by reason of any such action, but What I do claimas new anal tie; sire to secure by Letters Patent, is:

1. The process of precipitation of metale from solution by introcluoingan electrc current at a plurality of points throughout a solution, andby regulatng the resistance thereto, producng and maintainng any desireddensity ot' current throughout the elecname to this specification.

c EDVVARD ROYAL HOLDEL E ti

